1. Field of the Invention
This invention relates to a solar water heater and particularly to a dual phase solar water heater in which solar energy is absorbed from radiation and from convection of air.
2. Description of the Prior Art
With the increased emphasis on conservation of energy derived from fossil fuels, as well as the cost of electrical power, the use of solar energy for heating water for commercial and domestic use has become of great interest. Many versions of solar panels are now available which utilize a collector or back plate with a grid of fluid conduits attached in a heat-conductive relationship to the plate. A transparent cover is generally placed over the panel to minimize re-radiation of collected heat. Such panels are relatively expensive and usually the initial investment in panels for water heating will require several years to amortize through savings in costs of other sources of energy. For a typical home or other building, solar energy is also being absorbed by the roof structure not covered by solar energy panels. In a building having an attic space, the air in this attic space will be increased in temperature due to conduction of the absorbed thermal energy through the roof. In the majority of buildings, the energy thus absorbed from the solar radiation is not only wasted but presents a problem in air conditioning of the building, requiring significant amounts of ceiling insulation to prevent heat flow to the room below. In many buildings, an exhaust fan is utilized to reduce the attic temperature to minimize losses of air conditioner efficiency. Thus, not only is this collected heat energy wasted, but additional costs are involved in getting rid of the heat.
Therefore, it is evident that a technique for obtaining useful work from the attic heat which would significantly increase the efficiency of the solar heating system is needed.